THE EFFECTS OF CYPROHEPTADINE ON VACUOUS JAW MOVEMENTS IN RATS - A COMPARISON WITH HALOPERIDOL AND CLOZAPINE

Classic neuroleptics produce a syndrome of vacuous jaw movements in ra ts, hut atypical neuroleptics such as clozapine do not, This syndrome has been offered as a rapid and inexpensive means of assaying novel an tipsychotic compounds for the production of early onset extrapyramidal side effects, Cyproheptadine is a serotonergic antagonist that has be en suggested for the treatment of schizophrenia, The present study com pared the effects of repeated administration of cyproheptadine with th ose of the classic antipsychotic haloperidol and the atypical antipsyc hotic clozapine in terms of their production of vacuous jaw movements. Rats were administered either tartaric acid vehicle or one of three d oses of each drug daily for a month. Once a week the rats were observe d for a B-minute period by two trained observers who recorded their va cuous jaw movements, Cyproheptadine produced elevations in vacuous jaw movements similar to those produced by haloperidol, but clozapine did not. These results indicate that cyproheptadine may be similar to cla ssic antipsychotics in the production of extrapyramidal symptoms in hu mans, and they underscore the usefulness of the vacuous jaw movement m odel of early onset extrapyramidal side effects.